Media query syntax for Reactjs

The answer given by Ferit turned out to be quite useful, however, it was only the example in class components, but it is usually difficult or cumbersome to apply that to functional components, and since sometimes it is problematic to transform a functional component to a class one, here I leave the example using Hooks

import React, { useState, useEffect } from 'react';

const App = () => {
  const [matches, setMatches] = useState(
    window.matchMedia("(min-width: 768px)").matches
  )

  useEffect(() => {
    window
    .matchMedia("(min-width: 768px)")
    .addEventListener('change', e => setMatches( e.matches ));
  }, []);

  return (
    <div >
      {matches && (<h1>Big Screen</h1>)}
      {!matches && (<h3>Small Screen</h3>)}
    </div>
  );
}

export default App;

You can make media queries inside React:

import React, { Component } from 'react';

class App extends Component {
  constructor(props) {
    super(props)
    this.state = { matches: window.matchMedia("(min-width: 768px)").matches };
  }

  componentDidMount() {
    const handler = e => this.setState({matches: e.matches});
    window.matchMedia("(min-width: 768px)").addEventListener('change', handler);
  }
  render() {
    return (
      <div >
      {this.state.matches && (<h1>Big Screen</h1>)}
      {!this.state.matches && (<h3>Small Screen</h3>)}
      </div>
    );
  }
}

export default App;

https://stackblitz.com/edit/react-cu8xqj?file=src/App.js

---

09-10-2021 Edit: replaced addListener with addEventListener as former was deprecated. Thanks to John Galt for letting us know by posting a comment.

If you have a special cases, when you need to get media query result inside you react app (for example, you want to show some component at mobile version), you can use helpers like react-responsive or react-media-hook.